Introduction to Electrically Assisted Forming - Electrically Assisted Forming - page 24

materials (e.g., nylons, rubbers, ceramics, or plastics) cannot withstand the mechani-
cal demands placed on these components (i.e., too soft or too brittle). Outweighing
these issues, in most cases, are the energy reduction benefits, decreased flow stress,
increased ductility, and reduced springback, that can be accomplished using the EAF
method. Some tooling designs devised to overcome issues with electric current inte-
gration to the forming process are described in Chap. 10 .
2.2 EAF Literature Review
Research investigating how electricity affects materials can be traced back to the
mid-twentieth century in Russia. Toward the later part of this century, this research
slowly began in the United States. Now, there are an increased number of universi-
ties and national laboratories which have begun to focus on some portion of the
EAF technique. An in-depth explanation into the history of EAF research will be
provided below.
In 1959, Machlin et al. [ 2 ] examined electricity's effect on group 1A salts (NaCl),
determining that an applied electric current significantly affected the material's
ductility, flow stress, and yield strength. Later, Nabarro [ 3 ] discussed electricity's
effect on metals as part of his topic in 1967. In 1969, Troitskii et al. [ 4 ] studied how
electrons influence dislocation motion and reproduction in different alloys of zinc,
tin, lead, and indium, concluding that pulsed electricity could lower the flow stress
within the materials. Years later, in 1982, Klimov et al. [ 5 ] explained that the effects
on a metal's structure from electricity are unrelated to those caused by Joule heating.
Moving forward, in 1988, a microstructure analysis was conducted by Xu et al. [ 6 ],
and it was discovered that a continuous electric current in titanium materials caused
the recrystallization rate and the grain size of the materials to increase. Next, Chen
et al. [ 7 , 8 ] developed a relationship between electric flow and the formation of
intermetallic compounds (Sn/Cu and Sn/Ni systems). Afterward, in 2000, Conrad et
al. [ 9 - 11 ] determined that very high-current density/short-duration electrical pulses
can affect the plasticity and phase transformations of metals and ceramics. In 2005,
Heigel et al. [ 12 ] examined the microstructural alterations in Al 6061 resulting from
direct current.
Within the past few years, much experimental research has been performed to
establish how electricity affects the mechanical behavior of different metallic alloys.
In 2007, Andrawes et al. [ 13 ] was able to conclude that electrical current can signifi-
cantly reduce the energy needed for uniaxial tensile deformation of Al 6061-T6511
without greatly heating the workpiece. Perkins et al. [ 14 ] studied the effects of a
continuously applied electric current on various alloys undergoing an upsetting pro-
cess and found that the electricity increased the amount of allowable compressive
deformation prior to fracture and lowered the required compressive forces. Again
in 2007, Ross et al. [ 15 ] examined the application of a continuously supplied elec-
tric current on tensile specimens, only to conclude that, although deformation forces
were reduced, the achievable elongation was decreased, leading to premature failure.